RICHMOND, Va. - Photos of a balding, stocky man believed to have robbed 25 banks in 13 states will be plastered on billboards around the country as authorities try to catch the "Granddad Bandit," the FBI announced Monday.

The agency recently traced the string of robberies back to a 2008 holdup of a SunTrust Bank in downtown Richmond. Since then, he is believed to have robbed banks all over the eastern and central U.S.

While it's not clear if the robber is actually a grandfather, agents said the name was devised to help law enforcement and the public easily identify the suspect.

"He just looks like everyone's granddad," said supervisory special agent Amanda Moran.

The "Granddad Bandit" is described as a 45-to-60-year-old white man, about 6 feet tall and 230 pounds, balding with short grayish hair on the sides. He usually wears wire-rimmed glasses, short-sleeved collared shirts and ball caps.

In most cases, he waits patiently in line and hands the teller a note. Sometimes, he gestures that he has a weapon, although agents say there is no indication he's ever actually used one. Once his demands are met, he takes the note and exits quietly, fleeing on foot.

"If he was standing behind you in the teller line while you're waiting for teller service you wouldn't give him a second look," Moran said. "He blends well with people, and his look reminds you of the fatherly granddad."

The FBI declined to say how much money they think the suspect has stolen.

The robber rarely conceals his face, which agents said is uncommon.

The digital billboards, which will run in more than 40 states, feature the robber's photo, a tip-line number and reward information.

The billboards have been used before for local and regional crime alerts, including previous efforts to catch the "Granddad Bandit," but the current campaign is the most widespread of its kind.

The Federal Bureau of Investigation also increased the reward for his capture to $25,000.

As many as 2,000 billboards could show the message, said Jeff Golimowski, a spokesman for The Outdoor Advertising Association of America, which is partnering with the FBI on the campaign.

So far, 36 FBI arrests in other cases have been directly linked to tips from billboards, agents said.